Title: Effect of Aggregate Types on Mortar Properties Produced with Geopolymer Binders
Author(s): Klaus-Juergen Huenger, David Kurth, Maria Brigzinsky
Publication: Symposium Paper
Appears on pages(s): 290-300
Keywords: alumino-silicate structures, industrial residues, mortar properties, sand types, Si/Al ratio
Alumino-silicate compounds (geopolymers) are important for alternative binders for mortars and concretes. Such systems normally have a solid (metakaolin, slag, ash) and a liquid (activator solution) component. A newly developed system here consists of a waste silicate material and an aluminate source, both with a very good solubility. Under the addition of water only, a structure formation process occurs to form an alumino-silicate network. The Si/Al ratio can be varied in wide ranges to produce binders with different properties.
It was very surprising that the mortar properties not only depend on the recipe, but also on the aggregate types. Different aggregate types (quartz, greywacke, rhyolite, diabas, basalt, granodiorite) were chosen to produce mortar bars. All components were intensively mixed dry or as a slurry. Already the sand component affects the workability, further the setting time, the strength development and, of course, the durability. The best results were obtained with quartz, the worst with diabase or basalt sands. Obviously, the chemical and mineralogical composition and therefore the soluble constituents of the sand under highly alkaline conditions affected the structure formation process of the alumino-silicate binder and therefore the mortar properties too. The observed effects have nothing to do with an Alkali-silica-reaction (ASR).